1. Field of the Invention
The invention relates to a rack shaft support device.
2. Description of the Related Art
A steering apparatus of a rack-and-pinion system contains a rack shaft support device for removing backlash between the rack and the pinion. In the rack shaft support device, a support yoke that can slide back and forth and a compression coil spring that biases the support yoke are accommodated in a retention hole provided in a housing. By the support yoke biased by the compression coil spring, the rack shaft is axially slidably supported and also the rack shaft is pushed toward the pinion shaft.
However, as wear of the sliding portions of the rack shaft and support yoke advances in a long-term use, the play of the support yoke in the back-forth direction increases. As a result, there is the risk of generation of a rattling sound. Accordingly, a support yoke gap compensation device for inhibiting the back-forth play of the support yoke has been proposed (see, for example, Japanese Patent Application Publication No. 2007-238089 (JP-A-2007-238089)).
This support yoke gap compensation device is provided with a support yoke having a fixing groove, a yoke spring that provides a biasing force for pushing the support yoke toward a rack bar, a first cam that is disposed at the rear surface of the support yoke and has a first incline surface, a fixing member that is fitted in the fixing groove and maintains a gap between the support yoke and the first cam, a second cam that has a second inclined surface opposite the first inclined surface and a first groove formed in the central portion, a yoke plug having a second groove formed in the central portion, and a torsion spring disposed in a space between the first groove and the second groove. When a gap forms between the rack bar and the pinion, the second cam is rotated by the extension of the torsion spring and the gap is compensated.
In JP-A-2007-238089, the yoke spring presses the second cam against the yoke plug via the first cam. Consequently, when the second cam rotates due to the action of the torsion spring, there is the risk of rotation of the second cam being inhibited by the effect of frictional force generated between the second cam and the yoke plug. As a result, there are cases in which rattling sound cannot be prevented. Therefore, although it is conceivable to eliminate the yoke spring, in such a case, fluctuations in the amount of backlash attributable to fluctuations in meshing between the pinion and rack shaft cannot be absorbed, thereby resulting in the risk of an excessive increase in steering resistance.